206,567 research outputs found
La chiave del calendario gregoriano
No full textdel R. M. Hugolino Martelli ...Drucker gemäss Bingen, Nicole: Philausone (1500-1660), Nr. 451Bogensignaturen: *-**, A-Z⁸, †²Druckermarke François Conrards auf Titelseit
Pseudo time reversal operators for the state of polarization
No full textThe existence of three generalized mirrors (Martinelli and Martelli, 2017) that compensate for the effects of birefringence in retracing optical circuits allows to develop a parallel with the time reversal properties. The Wigner time reversal operator for the photon spin is considered and three pseudo time reversal operators borrowed from this original operator are introduced and analysed. Their application to different birefringence situations demonstrates the validity and the fertility of the approach
Transition Between Open and Closed Wake in 3D Linear Aerospike Nozzles
No full textLinear aerospike nozzles are envisaged as a possible device able to improve launcher engine performance. One of the most interesting properties of these nozzles is the possibility of a good integration with the vehicle. Tb improve the knowledge of the flow-field and performance of aerospike nozzles, they are studied numerically, with particular attention to the differences between the basic two-dimensional nozzle, usually considered in the design phase, and the more realistic three-dimensional nozzle. The study considers different plug lengths and ambient pressures to assess the role of the linear plug side truncation on the base pressure behavior. Numerical tests are carried out at supersonic flight Mach number. Copyright © 2005 by M. Geron and R. Paciorri.F. Nasuti, F. Sabetta, E. Martelli
Parameter Identification of a Model Scale Ship Drive Train
No full textSimulation models of the ship propulsion system play an increasingly important role, for instance in controller design and condition monitoring. However, creation of such simulation models requires significant time and effort. In this paper, the application of deterministic identification techniques on a DC-electric ship drive train is explored as an alternative for data-driven identification techniques that require extensive measured data sets collected over long periods of ship operation. First, a nonlinear and a linear simulation model that represent the dynamic behavior of the propulsion plant are developed, and the main parameters to be identified are defined. Then, a set of experiments on a model scale boat in the bollard pull condition are conducted using an ad hoc experimental setup and data acquisition system. Subsequently, various types of identification techniques are applied, aiming to determine the unknown model parameters. Eventually, a comparison is made between experimental and simulated results, using the different sets of the estimated parameters. The value of the demonstrated approaches lies in the fast determination of unknown system parameters. These parameters can be used in simulation models, which in turn can be used for various purposes such as system controller development and tuning. Furthermore, periodic determination of system parameters can support condition monitoring to detect faults or degradation of the system. The latter point directly deals with the condition-based maintenance issue; in fact, monitoring the propulsion plant parameters over time could allow for better management (and timing) of maintenance. Although the developed ideas are far from ready to be used on the full-scale, the authors believe that the methodologies are promising enough to be developed further towards a full-scale application.Ship Design, Production and Operation
Achille Martelli, voce biografica
No full textVoce biografica del pittore garibaldino d'origine calabrese Achille Martelli, attivo nel secondo Ottocento a napoli e in Calabria, al fianco di Andrea Cefaly e Michele Lenz
Numerical analysis of film cooling in advanced rocket nozzles
No full textThe key demand on future space transportation systems is the concurrent reduction of Earth-to-orbit launch costs and increase of launcher reliability and operational efficiency. A common way of slightly improving performance of gas-generator open-cycle engines is the injection of the turbine exhaust gas into the nozzle divergent section, which is also used for wall film cooling. The present study focuses on a numerical parametric analysis of the film-cooling efficiency in dual-bell nozzles. The secondary gas injection is made in the first bell, and it is found that the expansion fan originating from the inflection helps the film to better protect the wall. The results of fully-attached-flow simulations are also used to study the influence of film cooling on the expected behavior of nozzle side loads during operation with separated flow in the second bell. Copyright © 2009 by E. Martelli, F. Nasuti, and M. Onofri
Telemaco Signorini e Diego Martelli: l'Europa in Toscana.
No full textRicostruzione dell'ambiente artistico fiorentino negli anni Cinquanta-Sessanta dell'Ottocento tramite le figure e le opere del pittore Telemaco Signorini e del critico d'arte Diego Martelli anche attraverso i rispettivi rapporti con l'ambiente culturale europeo, fra Parigi e Londra
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